here @navinkumar21 is right and having the same problem and here is network does not have any issue.
i am facing this isse for last 1-2 week
in middle for this 1-2 week some days it worked but starting form yesterday it again the same problme

We have been observing limited traffic and some other anomalies from users of JIO for more than one week already - this is why I asked you about the operator in first place. Since the beginning we are doing our best to let our users browse the Internet freely back again, this is why you were able to use Mini during last weekend.

Yesterday we decided to turn off the compression for JIO and to force direct connection instead. Could you, please, switch to automatic mode and let me know if it helps?

I'm facing same problem.
I tried to sync my Speed Dials & Bookmarks by signing in my Opera Account from Opera Mini's setting. After logging in I go to https://sync.opera.com and saw that nothing was synced at all. While I have more than 10 Speed Dials, 5 Bookmarks on my device but at the Opera Sync service I found nothing.
Currently using; Opera Mini 37.4.2254.133967 on Android 6.1
Using both WiFi & 3G network connection and this problem remains whatever mode I'm on Opera Mini.
Please, fix this ASAP

I am using Opera Android and also am having problem with sync not working.
I have installed Opera on a new device and cannot acces speed dial and bookmark data on other devices to sync.
Logging in to sync opera.com shows nothing is being stored.
Is there a problem with opera's servers or not?